A Nifty Interactive Feature on the History of US Newspapers

Interactive map based on Library of Congress holdings and records.
You can move forward year by year (laborious) or advance the
interpretative panels on the right side (by era or decade).
You can move the map north, south, east or west.
You can zoom in on a city or area.
You can sort by language.
You can sort by publication frequency.
You can look at a detail list of newspapers on the bottom right for any city.